Problem: Christopher has walked his dog for a total of $20$ kilometers since he started walking daily. He has been walking $10$ kilometers each day. For how many days has Christopher been walking?
Solution: The number of days that Christopher has been walking is the total number of kilometers walked divided by the number of kilometers walked each day. $20\text{ kilometers} \div 10\text{ kilometers per day} = \text{number of days walking}$ $20\text{ kilometers} \div 10\text{ kilometers per day} = 2\text{ days}$